Are there two sine and cosine ratios?

[krahny]

When I enter sin(0) in a calculator, it gives me 0, and sin(90) gives me 1, just like I'd expect it to. But, when I use javascripts Math.sin() and Math.cos() functions, they give me completely different results. I think they might have something to do with pi, instead of an angle.

Could someone please help me?

Thanks.

[lemon-tree]

In Javascript (and PHP) the input for the sin functions are in radians rather than degrees. A radian is just a different way of measuring angles and is linked to circular calculations. There are 2pi radians in a complete circle, so 360˚ = 2pi radians and 180˚ = pi radians. The simplest way to convert one to the other is like so:

If you intend to do this:
Math.sin(number);
Change it to this:
Math.sin((Math.PI * number)/180);

Also remember that doing inverse sin functions will give you an answer in radians that you may then want to convert to degrees.

[leafypiggy]

lemon-tree: This is actually true for calculators too. Their default setting is Radian, however most schools make kids change the setting to Degree so they don't run into this problem. :P

[lemon-tree]

Wasn't the default on my lump of a calculator, at least I don't think it was. Don't fancy resetting it to test and lose the data on it.

[descalzo]

My first calculator:

[lemon-tree]

Retro
Anyway, krahny is this working for you now? If you need any further explanation of the the implementation or the theory then one of us will be happy to help.

[essellar]

@descalzo: What's that, a 45 maybe? I have no idea how old you are, but I remember paying more for my first HP than I paid for my first (used) car. Never could get the hang of RPN -- I became a TI man by '77 (the TI 59 was another half-a-grand machine when I bought it). And, to get back to the question at hand, it defaulted to degree mode as well.

[descalzo]

HP 35. Originally ('72) cost $395 (about $2000 in today's dollars). Was at U.C. Berzerkly.

Considering the laptop/notepad you can get today for $395 it is mind boggling.

[essellar]

Ah, a fellow fogie. Good to know I'm not the only one. (And I'd bet we're the only ones here who remember Al Capp's characters. Schmoo's cool, but I was into Joe Btfsplk -- he kinda reminded me of me. And as a Canadian, often standing waist-deep or deeper in the snow, I had a deep feeling of kinship with the good people of Lower Slobovia.)

[krahny]

Thanks, Lemon-tree, that code worked.